Multicolor photographic element comprising an oxacyanine sensitizing dye

ABSTRACT

Photosensitivity of a blue-sensitive emulsion in a multicolor diffusion transfer photographic system may be increased by sensitizing that emulsion with a member of a class of oxacyanine dyes.

United States Patent Inventor Alan E. Rosenoff Waltham, Mass. App]. No. 880,684 Filed Nov. 28, 1969 Patented Oct. 26, 1971 Assignee Polaroid Corporation 7 Cambridge, Mass,

MULTICOLOR PHOTOGRAPHIC ELEMENT COMPRISING AN OXACYANINE SENSITIZING DYE 9 Claims, 10 Drawing Figs.

U.S. Cl ..96/77, 96/3, 96/29 D, 96/106 Int. Cl 603C 7/00, G030 1/40, G03'c [/16 Field of Search 96/106, 3, 7 7, 29 D [56] References Cited UNITED STATES PATENTS 2,108,485 2/1938 Hamer 96/106 X 2,143,839 1/1939 Brooker 96/106 X 2,189,599 2/1940 Brooker 96/106 X 2,241,237 5/1941 Brooker 96/106 X Primary Examiner- Norman G. Torchin Assistant Examiner-Alfonso T. Suro Pico An0rneys-Brown and Mikluka and Sheldon W Rothstein ABSTRACT: Photosensitivity of a blue-sensitive emulsion in a multicolor diffusion transfer photographic system may be increased by sensitizing that emulsion with a member of a class of oxacyanine dyes.

PATENTEnncr 26 191: 3,615,543

sum lUF 2 INVENTOR. ALAN E. ROSENOFF 614mm W m ATTORNEYS PATENTEUum 26 Ian 3,61 5 543 SHEET 2 c.= 2

INVENTOR. ALAN E. ROSEmFF E/wum WW4.

6151140 n am arromvcvs MULTICOLOR PHOTOGRAPHIC ELEMENT COMPRISING AN OXACYANINE SENSlTlZING DYE present invention relates to photography and, more particularly, to photographic products particularly adapted for employment in photographic diffusion transfer color processes.

BACKGROUND OF THE INVENTION As disclosed in U.S. Pat. No. 2,983,606, issued May 9, 1961, a photosensitive element containing the image-receiving dye developer that is, a dye which is a silver halide developing agent, and a silver halide emulsion, may be exposed to actinic radiation and wetted by a liquid development of composition, for example, by immersion, coating, spraying, flowing etc., in the dark, and the exposed photosensitive element is superposed prior to, during, the latent after wetting, on a sheetlike support element which may be utilized as an image-receiving element. In a preferred the dye disclosed therein, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid processing composition, positioned intermediate the photosensitive element and the image-receiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. In exposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by diffusion, to a superposed image-receiving layer or element, said transfer substantially excluding oxidized dye developer. The iamge-receiving element receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide the reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. In one disclosed preferred embodiment, the desired positive image is revealed by stripping the image-receiving layer from the photosensitive element at the end of a suitable imbibition period.

The dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function" is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

Multicolor images may be obtained using color image-forming components such as, for example, the previously mentioned dye developers, in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned U.S. Pat. No. 2,983,606, and particularly with reference to FIG. 9 of the patent's drawing, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion layer, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata are disclosed to be optionally separated from other sets by suitable interlayers, for example, by a layer of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be employed. ln such instances, a separate yellow filter may be omitted.

The dye developers are dye image-forming materials which are preferably selected for their ability to provide colors that are useful in carrying out substractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective silver halide emulsion. Specifically, the dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution about 0.5 to 8 percent by weight, of the respective dye developer distributed in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diffusion transfer fluid processing composition An extensive compilation of specific dye developers particularly adapted for employment in photographic diffusion transfer processes is set forth in aforementioned U.S. Pat. No.

2,983,606, and in the various copending U.S. applications referred to in that patent, especially in the table of U.S. applications incorporated by reference into the patent as detailed in column 27. As examples of additional U. S. patents detailing specific dye developers for photographic transfer process use, mention may also be made of U.S. Patents Nos. 2,983,606; 2,992,106; 3,047,386; 3,076,808; 3,076,820; 3,077,402; 3,126,280; 3,13l,06l; 3,134,762; 3,l34,765; 3,l35,604; 3,135,605; 3,135,606; 3,135,734; 3,l4l,772; 3,142,565; and the like.

As additional examples of synthetic, film-forming, permeable polymers particularly adapted to retain dispersed dye developer, mention may be made of nitrocarboxymethyl cellulose, as disclosed in U.S. Pat. No. 2,992,104; an acylamidobenzene sulfo ester of a partial sulfobenzal of polyvinyl alcohol, as disclosed in U.S. Pat. No. 3,043,692; polymers of N-alkyl-a,B-unsaturated carboxamides and copolymers of N-alkyl-mBcarboxamides with N-hydroxyalkyl-afi-unsaturated carboxamides, as disclosed in U.S. Pat. No. 3,069,263; copolymers of vinyl-phthalimide and a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,061,428; copolymers of N-vinylpyrrolidones and afi-unsaturated carboxylic acids and terpolymers of N-vinyl-pyr-- rolidones, a,B-saturated carboxylic acids and alkyl esters of a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,044,873; of N,N-dialkyl-a,B-unsaturated carboxamides with afi-unsaturated carboxylic acids, the corresponding amides of such acids, and copolymers of N-aryland N-cycloalkyl-a,/3- unsaturated carboxamides with a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,069,264; and the like.

In addition to conventional techniques for the direct dispersion of a particulate solid material in a polymeric, or colloidal, matrix such as ball-milling and the like techniques, the preparation of the dye developer dispersion may also be obtained by dissolving the dye in an appropriate solvent, or mixture of solvents, and the resultant solution distributed in the polymeric binder, with optional subsequent removal of the solvent, or solvents, employed as, for example, by vaporization where the selected solvent, or solvents, possesses a sufficiently low boiling point or washing where the selected solvent, or solvents, possesses a sufficiently high differential solubility in the wash medium, for example, water, when measured against the solubility of the remaining composition components and/or obtained by dissolving both the polymeric binder and dye in a common solvent.

For further detailed treatment of solvent distribution systems of the types referred to above, and for an extensive compilation of the conventional solvents traditionally employed in the art to effect distribution of photographic colorproviding materials in polymeric binders, specifically for the formation of component layers of photographic film units, reference may be made to U.S. Pat. Nos. 2,269,158; 2,322,027; 2,304,939; 2,304,940; 2,801,171; and the like U.S. pat. No. 3,362,819 discloses image-receiving elements, particularly adapted for employment in the preceding diffusion transfer processes, which comprise a support layer possessing on one surface thereof, in sequence, a polymeric acid layer, preferably an inert timing or spacer layer, and an imagereceiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance.

As set forth in the last-mentioned patent, the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium potassium, etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acid-yielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. The acid-reacting group is, of course, nondiffusible from the acid polymer layer. in the preferred embodiments disclosed, the acid polymer contains free carboxyl groups and the transfer processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, beinginsoluble in water in the free acid form, and by forming watersoluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anhydride groups, at least some of which preferably have been converted to free carboxyl groups prior to inhibition While the most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used. As examples of specific polymeric acids set forth in the application, mention may be made of dibasic acid halfester derivatives of cellulose modified with sulfoanhydrides, e.g., with ortho-sulfobenzoic anhydride; polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxy or sulfo-substituted aldehydes, e.g., M-, or p-benzaldehyde sulfonic acid or carboxylic acid; partial esters of ethlenelmaleic anhydride copolymers; partial esters of methyl-vinyl ether/maleic anhydride copolymers, etc.

The acid polymer layer is disclosed to contain at least sufficient groups to effect a reduction in the pH of the image layer from a pH of about 13 to 14 to a pH of at least 11 or lower at the end of the imbibition period, and preferably to a pH of about 5 to 8 within a short time after imbibition. As previously noted, the pH of the processing composition preferably is of the order of at least 13 to 14.

it is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or image transfer of unoxidized dye developers. For this reason, the pH of the image layer is kept at a level of pH 12 to 14 until the positive dye image has been formed, after which the pH is reduced very rapidly to at least about pH 1 l, and preferably about pH 9 to 10, which renders unoxidized dye developer substantially nondifi'usible. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the positive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and it is necessary that the pH of the image layer remain on the order of 12 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pH reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer. This processing technique thus efi'ectively minimizes changes in color balance which might result from a longer than necessary imbibition time for multicolor transfer processes using multilayer negatives.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, by an undesired reduction in positive image density, the acid groups are disclosed to be so distributed in the acid polymer layer that the rate of their availability to the alkali which acts controllable, e.g., as a function of the rate of swelling of the polymer the polymer which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired distribution of the acid groups in the acid polymer layer may be effected by mixing the acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, or by using only the acid polymer but selecting one having a relatively lower proportion of acid groups. These embodiments are illustrated, respectively, in the cited patent by (a) a mixture of cellulose acetate and cellulose acetate hydrogen phthalate and (b) a cellulose acetate hydrogen phthalate polymer having a much lower percentage of phthalate groups than the first-mentioned cellulose acetate hydrogen phthalate.

it is also disclosed that the layer containing the polymeric acid may contain a water insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats may be employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer of the aforementioned patent, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to time" control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. it was stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer, but thepH drops quite rapidly once the alkali difiuses through the spacer layer. Other such spacer layers which are suitable for use in the image-receiving element are disclosed and claimed in U.S. Pat. No. 3,421,893.

As examples of materials for use as the image-receiving layer, mention may be made of solution dyeable polymers such as nylons as, for examples, N-methyoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with fillers as, for example, one-halt cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine. sodium hydroxide or sodium carbonate and the like, and preferably possessing a pH in excess of i2 and most preferably, a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric water-soluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally film-forming materials or thickening agents whose ability to increase viscosity is substantially unaffected if let in solution for a long period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 cps. at a temperature of approximately 24 C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

For the production of the photoresponsive gelatino silver halide emulsions employed to provide the film unit, the silver halide crystals may be prepared by reacting a water-soluble silver salt, such as silver nitrate, with at least one water-soluble halide, such as ammonium, potassium or sodium bromide,

' preferably together with a corresponding iodide, in an aqueous solution of a peptizing agent such as colloidal gelatin solution; digesting the dispersion at an elevated temperature, to provide increased crystal growth; washing the resultant dispersion to remove undesirable reaction products and residual water-soluble salts by chilling the dispersion, noodling the set dispersion, and washing the noodles with cold water, or, alternatively, employing any of the various flocc systems, or procedures, adapted to effect removal of undesired components for example, the procedures described. in U.S. Pat. Nos. 2,614,928; 2,614,929; 2,728,662; and the like; afterripening the dispersion at an elevated temperature in combination with the addition of gelatin and various adjuncts, for example, chemical sensitizing agents of U.S. Pat. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; and the like; all according to the traditional procedures of the art, as described in Neblette, C. 8., Photography lts Materials and Processes, 6th Ed., 1962.

Optical sensitization of the emulsion 's silver halide crystals, toward which the instant invention is directed, may be accomplished by contact of the emulsion composition with an effective concentration of the selected optical sensitizing dyes dissolved in an appropriate dispersing solvent such as methanol, ethanol, acetone, water, and the like; all according to the traditional procedures of the art, as described in Hammer, F. M., The Cyanine Dyes and Related Compounds.

Additional optional additives, such as coating aids, hardeners, viscosity-increasing agents, stabilizers, preservatives, and the like, for example, those set forth hereinafter, also may be incorporated in the emulsion formulation, according to the conventional procedures known in the photographic emulsion manufacturing art.

The photoresponsive material of the photographic emulsion will, as previously described, preferably comprise a crystal of silver, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide or silver iodobromide, of varying halide ratios and varying silver concentrations.

The emulsions may include the various adjuncts, or addenda, according to the techniques disclosed in the art.

As the binder for the respective emulsion strata, the aforementioned gelatin may be, in whole or in part, replaced with some other colloidal material such as albumin; casein; or zein; or resins such as a cellulose derivative, as described in U. S. Pat. Nos. 2,322,085 and 2,327,808; polyacrylamides, as described in U.S. Pat. No. 2,541,474; vinyl polymers such as described in a multiplicity of readily available U.S. Patents.

In accordance with U.S. Pat. Nos. 3,415,644, 3,415,645 and 3,415,646, an image-receiving element need not be separated from superposed contact with a photosensitive element comprising a silver halide emulsion subsequent to substantial transfer image formation if the image-receiving element is transparent and a processing composition containing a substance'rendering the processing composition layer opaque is spread between the image-receiving layer and the photosensitive element.

Specifically, an integral diffusion transfer photographic film unit particularly adapted for the production of a dye transfer image of improved stability will be constructed, for example, in accordance with aforementioned U.S. Pat. No. 3,415,644 to include a photosensitive element comprising a laminate having in sequence as essential layers, a dimensionally stable opaque support layer, a photosensitive silver halide emulsion layer having associated therewith dye image-providing material which is soluble and diffusible in alkali at a first pH, an alkaline solution penneable polymeric layer dyeable by the dye image-providing material, a polymeric acid layer containing sufi'rcient acidifying material to effect reduction subsequent to substantial transfer dye image formation of a processing solution having the first pH to a second pH at which said dye image-providing material is insoluble and nondiffusible, and a dimensionally stable transparent support layer, said dimentionally stable support layers comprising extremities of the described photographic film unit composite structure. 1n combination with the laminate a rupturable container retaining an aqueous alkaline processing composition having the first pH and containing an opacifying agent in a quantity sufficient to mask the dye image-providing material, is fixedly positioned and extends transverse the leading edge of the laminate whereby to effect unidirectional discharge of the containers contents between the alkaline solution permeable and dyeable polymeric layer and the photosensitive silver halide emulsion layer next adjacent thereto upon application of compressive force to the container.

Employment of such film units according to the described color diffusion transfer photographic process specifically provides for the production of a highly stable color transfer image accomplished at least in part by in process adjustment of the environmental pH of the film unit from a pH at which transfer processing is operative through a pH at which dye transfer is inoperative subsequent to substantial transfer image formation. The stable color transfer image is obtained irrespective of the fact that the film unit is maintained as an intregal laminate during exposure, processing, viewing and storage and such transfer image exhibits the required maximum and minimum dye transfer image densities, dye saturations, hues, definition, etc. It should, however, be recognized that film units fabricated in accordance with the parameters set forth directly above specifically require the presence of the stated neutralizing component disclosed in U.S. Pat. No. 3,362,819 to effect in situ process adjustment of the film units operational pH range thereby terminating the transfer process at such time as the appropriate transfer image has been formed in the image-receiving element.

In numerous multicolor photographic difiusion transfer systems, it is desirable to utilize, integral, with the photosensitive element thereof, in a layer more distal from the photosensitive element support layer than any of the photosensitive emulsion layers, an ultraviolet light absorbing composition. It will be appreciated that such composition will remove spectral components of incident radiation which generally stimulate response in the inherently sensitive region of photosensitive silver halide emulsions, that is, in the blue and violet portions of the spectrum. ln order to regain the color balance that may be lost due to the incorporation of such an ultraviolet light absorbing composition in the photosensitive element, it has been found necessary to also incorporate in such element a mechanism which will potentiate the efiect of radiation within the blue portion of the visible spectrum which is incident upon the particular emulsion designed to be responsive to such radiation. 1t has been unexpectedly found that a certain class of oxacyanine dye materials, as more fully described hereinbelow, may be satisfactorily utilized in a multicolor diffusion transfer photographic system in conjunction with an ultraviolet light absorbing composition and will potentiate the effect of incident radiation within the blue portion of the spectrum on the appropriate photosensitive emulsion to the extent that sufficient blue speed may be achieved to provide the development, an appreciable antifoggant effect, and improved lumination latitude.

OBJECTS or THE INVENTION The primary objects of the present invention are to provide photographic products particularly adapted for employment in photographic difiusion transfer color processes; to provide photographic products which include a photosensitive ele- 1 ment which comprises at least two selectively sensitized photosensitive strata at least one of which contains an oxacyanine sensitizing agent, said photosensitive strata being associated with dyes of predetermined color which are silver halide developing agents and are separated each from the other by a suitable interlayer; to provide photographic diffusion transfer products comprising photosensitive element of the last-identified type which additionally includes an ultraviolet absorbing material in a layer superposed on said photosensitive strata wherein said oxacyanine sensitized layer is capable of potentiating the effect of incidentradiation within the blue portion of the visible spectrum whereby color balance of the I ultimate image is unefi'ected; and to provide photographic diffusion transfer color images and processes which possess improved lamination latitude, substantial latent image stabilization, and antifoggant functionality.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the other which are exemplified in the following detailed disclosure, and the scope of the application of which will be in dicated in the claims.

For a further understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein FIGS. 1 through 5 are reproductions of wedge spectograms of iodobromide silver halide emulsions sensitized with various materials within the context of the present invention; and FIGS. 6 through 10 are reproductions of latent image stabilization density studies which demonstrate the latent image stabilization effect produced by a typical compound of the present invention at various levels with respect to the silver present in the system.

BRIEF SUMMARY OF THE INVENTION It has been discovered that the sensitivity to the blue portion of the visible spectrumof a silver halide photosensitive emulsion utilized in a diffusion transfer photographic environment representative embodiments and photographic utilization of the novel photosensitive elements of this invention which,

in conjunction with a dye developer may be enhanced by incorporating into said emulsion an oxacyanine sensitizing dye of the formula:

R C=C alkylene l alk ldene 1 wherein R and R are each' hydrogen or acid functional groups, such as, preferably, SO,H; CO,H; -SO,'; and CO wherein not more than one of said R and R may be hydrogen; R and R are alkyl, alkoxy, halogen, or hydrogen; and the alkylene groups denoted contain between I and [8 carbon atoms, inclusive.

DETAILED DESCRIPTION OF THE INVENTION It will be appreciated that the essence of the present invention resides in the utilization of a particular class of oxacyanine dye sensitizers for the enhancement of the blue response in a typical diffusion transfer photosensitive system as described above. It will be appreciated that such enhancement is advantageous to diffusion transfer photography due to the above-denoted thinness of the silver halide emulsion layers utilized and the possible utilization of an ultraviolet light abi sorbing material which removes much of the electromagnetic radiation which would ordinarily stimulate latent image formation in the blue-sensitive emulsion. The preferred material utilized in the context of the present invention is 3-carboxymethyl-l-ethyloxa-2-cyanine bromide Sensitizing materials of the present invention are incorporated into the emulsion by well-known techniques as, for example, by being distributed uniformly throughout a washed, finished emulsion in a concentration dependent on the sensitometric characteristics of the particular emulsion and the effects desired, as hereinabove denoted. Ordinarily, best results may be obtained in about a 'ratio of 1 mg. of dye per gram of silver. However, it is generally conceded that ratios between 0.05 mg. of dye to 4.0 mgs. of dye per gram of silver may be employed. Preferably the dyes are added to the emulsion, in a suitable solvent as, for example, methanol, ethanol, etc., slowly and under constant stirring. The sensitized emulsion may be handled, stored and coated thereafter according to conventional techniques.

The present invention will be illustrated in greater detail in conjunction with the following procedures which set out however, are not limited to the details set forth therein and are intended to be illustrative only.

EXAMPLE 2-5 Using the same reaction denoted above, 3-carboxymethyll 3-sulfopropyl)-oxa-2-cyanine betaine is prepared utilizing 3-carboxymethyl-Z-methylbenzoxazolinium bromide and l- (3-sulfopropyl)-2-phenylthioquinolinium betaine as starting materials; 3-carboxymethyl-l '-ethyloxa-2'-cyanine bromide is prepared utilizing l-ethyl-2-phenylthioquinolinium mesylate and 3-carboxymethyI-Z-methylbenzoxazolinium bromide as starting materials; 3-(3-sulfopropyl)-1'-ethyloxa-2'-cyanine betaine is prepared utilizing 3-(3-sulfopropyl-2- methylbenzoxazolinium betaine and l-ethyl-2-methylbenzoxazolinium betaine and l-ethyl-2-phenylthioquinolinium mesylate as starting materials; and 3-carboxymethyl-l'-ethyl-6-methoxyoxa-2-cyanine bromide is prepared utilizing 6- methoxy-lethyl2-phenylthioquinolinium tosylate and 2 -methyl-3-carboxymethylbenzoxazolinium bromide as starting materials.

2 EXAMPLE 6 A monochromatic photosensitive element was prepared film coating, in succession, on a gelatin subcoated cellulose triacetate folm base the following layers: 1. a layer of the yellow dye developers 4-(p-[fi-hydroquinonyl ethyl]-phenylazo)- 3-(N-n-hexylcarboxamido)-l-phenyl-S-pyrazolone dissolved in diethyl lauramide dispersed in gelatin and coated at a coverage of about 30 mgs./ft. of dye and about 40 mgs./ft. of gelatin; and 2. a blue-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 90 mgs./ft. of silver and about 65 mgs./ft. of gelatin.

Additional photosensitive elements substantially of the lastidentified type were fabricated wherein the blue-sensitive iodobromide emulsion additionally contained:

l. 1 mg. of 3-carboxymethyl-l -ethyloxa-2'-cyanine bromide per gm. of silver;

2. 0.976 mg. of 3-carboxyethyl-l-ethyloxa-2'-cyanine bromide per gm. of silver;

3. l.03mgs. of 3-carboxymethyl-l-(3-sulfopropyl)-oxa-2'- cyanine betaine per gm. of silver; and

4. 1.07 mgs. of 3-carboxymethyl-l'-ethyl-6'-methoxyoxa-2 '-cyanine bromide per gm. of silver.

Typical diffusion transfer image-receiving elements were then fabricated by coating a cellulose nitrate subcoated baryta paper with the partial butyl ester of polyethylene-maleic anhydride copolymer prepared by refluxing for 14 hours 300 grams of high viscosity poly-(ethylene/maleic anhydride), I40 grams of N-butyl alcohol and l cc. of 85 percent phosphoric acid to provide a polymeric acid layer approximately 0.75 mil. thick. The external surface of the acid layer was then coated with a 4 percent solution of polyvinyl alcohol in water to provide a polymeric spacer layer approximately 0.30 mils. thick. The external surface of the spacer layer was then coated with a 2:l mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine at a coverage of approximately 600 mgs./ft. to provide a polymeric image-receiving layer. The thus prepared image-receiving element is then baked at l80 F. for 30 minutes and allowed to cool.

Each of the above-denoted photosensitized monochromes were exposed to filtered electromagnetic radiation through a step wedge in a spectraograph and processed by spreading an aqueous liquid processing composition comprising:

Water I cc.

Potassium hydroxide ll.2 g.

Hydroxyelhylccllulose 3.9 g.

(high viscosity) Potassium thiosulfatc 0.5 g.

Benzotriazole 3.5 g.

N-benzyl-a-picolinium bromide 2.0 g.

between an image-receiving element and each of the exposed photosensitive monochromatic elements as they were brought into superposed relationship. After an imbibition period of approximately l minute, the image-receiving elements were separated from the remainder of the film assembly and the resultant spectrograms are reproduced in FIGS. 1 through 5. FIG. 1 denotes the inherent sensitivity of the emulsion utilized. It will be appreciated that increased sensitivity is predominant in FIGS. 2, 3, 4 and 5 due to the addition of the denoted sensitizing materials within that class of materials forming the subject matter of the present invention.

It will be further noted that peak sensitivity is produced between approximately 495 and 505 nanometers depending upon the particular sensitization material utilized.

It has been found from develographic data produced with emulsions comprising sensitizing dyes of the class denoted herein that the induction time, that is, the time period between processing solution contact and initiation of development of photoexposed silver halide, is substantially reduced when compared with photosensitive emulsions not containing the compounds of the present invention. This unexpected side effect has an obvious advantage in diffusion transfer photography in that color image control is substantially wholly provided by the developed silver halide emulsion. After inhibition of the processing composition into the photosensitive unit, dye which is initially solubilized tens to migrate and, depending upon the degree of control exercised by the emulsion at any given time, may pass through the emulsion layer before suflicient development has been achieved to inhibit the passage of such materials. While in conventional photographic processes of slight reducton in induction time is not particularly advantageous, it will be appreciated that in diffusion transfer systems, even minute reductions in induction time are quite valuable.

Other experiments have demonstrated that the compounds of the present invention provide improved luminescence latitude and somewhat of an antifogging effect to the emulsions in which they are incorporated.

EXAMPLE 7 It has been alluded to above that substantial latent image stability has been discovered as a significant side effect in the utilization of the blue-sensitizers of the class denoted in the present invention Monochromatic photosensitive elements were prepared by coating, in succession, onto a gelatin subcoated cellulose triacetate film base the following layers:

1. a layer of magenta dye developer Z-(p-[a-hydroquinonylethyll-phenylazo)-4-isopropoxy-l-naphthol dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of about 30 mgs./ft. of dye and about 65 mgs./ft. of gelatimand 2. a green-sensitive gelatino silver iodobromide emulsion coated at a coverage of about mgs./ft. of silver and about 55 mgs./ft. of gelatin.

Subsequent photosensitive monochromes of the aboveidentified type were fabricated wherein the green-sensitive gelatino silver halide emulsion contained varying levels of 3- carboxymethyl-l'-ethyloxa-2'-cyanine bromide including 0.l mg., 0.5 mg., l.0 mg., and L4 mgs. per gm. of silver, respectively. The fresh coatings on each of the above-denoted monochromes were uniformly exposed through a vertical step wedge. The exposed materials where then placed in an accelerated aging atmosphere by being held .under approximately 52 atmospheres pressure for a week in order to simulate about one year's aging. Subsequently, a horizontal exposure was made through a step wedge and the photosensitive monochromes were developed in accordance with the technique described in the example next above. Reproductions of the images produced in the image-receiving elements utilized with the above respective monochromes are denoted in FIGS. 6 through l0. Direct visual observation demonstrates that the monochrome containing no blue-sensitizers shows poor latent image stability with the increasing latent image stability being progressively evident up to a level of L0 mg. of sensitizer dye per gm., of silver, which appears to represent a balance between latent image regression and latensification, the former being a relative loss of latent image as a function of time while the latter is a relative gain in latent image as a function of time.

It has been found that sensitized silver halide emulsions utilizing dye materials of the herein denoted class do not lose spectral sensitization, i.e., are not antisensitized, in the presence of dye couplers and other materials commonly utilized in diffusion transfer photographic systems. However, in order to assure proper sensitizer adsorption and no antisensitization at least one of the R or R denoted moities with the class of materials disclosed must be acid functional.

it will further be appreciated that a requisite function of the dye sensitizers of the present invention is that they be nonmigratory-for were they to ditTuse, they might provide a chromatically deleterious effect to any ultimate image formed. In general, the migration propensities of the denoted sensitizers may best be controlled by choosing appropriate alkylene groups in the generic formula above. With further regard to such formula, the moieties denoted as R and R comprise conventional cyanine dye substituents as defined in Hamer, above, the selection of which is made by the operator It will be noted that the liquid processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methylaminophenol, 2,4-diamino-phenol, pbenzylaminophenol, hydroquinone, toluhydroquinine, phenylhydroquinone, 4'-methylpyenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary of accelerating developing agents, such as a 3-pyrazolidone developing agent and a benzenoid developing agent, as disclosed in U.S. Pat. No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of l-phenyl-3-pyrazolidone in combination with pbenzylaminophenol and l-phenyl-3-pyrazolidone in combination with 2,5-bis-ethyleneimino hydroquinone. Such auxiliary developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in any one or more of the silver halide emulsion strata, the strata containing the dye developers, the interlayers, the overcoat layer, the image-reeeiving layer, or in any other auxiliary layer, or layers, of the film unit. It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silver halide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

ln addition, development may be effected in the'presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed in U.S. Pat. No. 3,173,786.

Although the invention has been discussed in detail throughout employing dye developers, the preferred dye image-forming materials, it will be readily recognized that other, less preferred, dye image-providing materials may be substituted in replacement of the preferred dye developers in the practice of the invention For example, there may be employed dye image-forming materials such as those disclosed in U.S. Pat. Nos. 2,647,049, 2,661,293, 2,698,244, 2,698,798, and 2,802,735, wherein color diffusion transfer processes are described which employ color coupling techniques comprising, at least in part, reacting one or more color developing agents and one more color formers or couplers to provide a dye transfer image to a superposed image-receiving layer and those disclosed in U.S. Pat. No. 2,774,668, wherein color diffusion transfer processes are described which employ the imagewise differential transfer of complete dyes by the mechanisms therein described to provide a transfer dye image to a contiguous image-receiving layer.

In products employed in the diffusion transfer processes of this invention, it may be preferable to expose from the emulsion side. In such instances, it is, therefore, desirable to hold the photosensitive element and the image-receiving element together at one end thereof by suitable fastening means in such manner that the photosensitive element and the imagereceiving element may be spread apart from their superposed processing position during exposure. A camera apparatus suitable for processing film of the type just mentioned is provided by the Polaroid Land Camera, sold by Polaroid Corporation, Cambridge, Massachusetts, or similar camera structure such, for example, as the roll film type camera forming the subject matter of U.S. Pat. No. '2,435,7 l 7 or the film pack type camera forming the subject matter of U.S. Pat. No. 2,991,702. Camera apparatus of this type permits successive exposure of individual frames of the photosensitive element from the emulsion side thereof as well as individual processing of an exposed frame by bringing said exposed frame into superposed relation with a predetermined portion of the imagereceiving element while drawing these portions of the film assembly between a pair of pressure member which rupture a container associated therewith and effect the spreading of the processing liquid released by rupture of said container, between and in contact with the exposed photosensitive frame and the predetermined, registered area of the image-receiving element.

It will be apparent that the relative proportions of the agents of the diffusion transfer processing composition may be altered to suit the requirements of the operator Thus, it is within the scope of this invention to modify the herein-described developing compositions by the substitution of preservatives, alkalies, silver halide solvents, etc., other than those specifically mentioned, provided that the pH of the composition is preferably in excess of at least 10 initially. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of various components may be varied over a wide range and when desirable adaptable components may be disposed in the photosensitive element, prior to exposure, in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The support layers referred to may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include paper; aluminum; polymethacrylic acid methyl and ethyl esters; vinyl chloride polymers; polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol terephthalic acid; and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate butyrate, acetate-propionate, or acetate-butyrate The nature and construction of rupturable containers is well understood in the art; see, for example, U.S. Pat. No. 2,543,181, issued Feb. 27, 1951, and U.S. Pat. No. 2,634,886, issued Apr. 14, 1953. I

It will be further apparent that, by appropriate selection of the image-receiving element materials from among suitable known opaque and transparent materials, it is possible to obtain either a colored positive reflection print or a colored posi tive transparency.

While a rupturable container provides a convenient means for spreading a liquid processing composition between layers of a film unit whereby to permit the processing to be carried out within a camera apparatus, the practices of invention may be otherwise effected. For example, a photosensitive element, after exposure in suitable apparatus and while preventing further exposure thereafter to actinic light, may be removed from such apparatus and permeated with the liquid processing composition, as by coating the composition on said photosensitive element or otherwise wetting said element with the composition, following which the permeated, exposed photosensitive element, still, without additional exposure to actinic light, is brought into contact with the image-receiving element for image formation in the manner heretofore described.

In all examples of this specification percentages of components are given by weight unless otherwise indicated.

In addition to the described essential layers, it will be recognized that the film unit may also contain one or more subcoats or layers, which, in turn, may contain one or more additives such as plasticizers, intermediate essential layers for the purpose, for example, of improving adhesion.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photosensitive element containing a plurality of essential layers including, in sequence:

a. a support layer;

b. a cyan dye-containing layer associated with a red-sensitive silver halide emulsion;

said blue-sensitive halide emulsion additionally including an oxacyanine dye of the formula:

I|-I alkrl lene alkyl lene R wherein R and R are hydrogen or acid-functional substituents, provided at least one of said R or R is an acid-functional substituent; and R and R are alkyl, alkoxy, halogen, or hydrogen.

2. The element of claim 1 wherein said acid functional substituent is SO ,H; CO H; --CO or -SO H.

3. The element of claim 2 wherein said oxacyanine dye is 3- carboxymethyl-l '-ethyloxa-2'-cyanine bromide.

4. A photographic film unit which comprises, in combination:

a photosensitive element having a diffusion transfer imagereceiving element affixed at least one edge thereof, said photosensitive element comprising, as essential layers:

a'. a support layer;

b. a cyan dye-containing layer associated with a red-sensitive silver halide emulsion;

c. a magenta dye-containing layer associated with a greensensitive silver halide emulsion;

d. a yellow dye-containing layer associated with a blue-sensitive silver halide emulsion, each of said cyan, magenta and yellow dyes being silver halide developing agents and said blue-sensitive silver halide emulsion additionally including an oxacyanine dye of the formula:

/O R R C=CH J III alkylene alk3l7lene it wherein R and R are hydrogen or acid-functional substituents, provided at least one of said R of R is an acid-functional substituent; and R and R are alkyl, alkoxy, halogen, or hydrogen;

said diffusion transfer image-receiving element comprising as essential layers, in sequence 1. a support layer, and

2. an alkaline processing composition permeable and dyeable layer wherein said photosensitive and said imagereceiving elements are adapted to be superposed, the support layers of each comprising the extremities of the superposed structure.

5. The element of claim 4 wherein said acid functional substituent is -SO;,; CQ,H; -CO and SO;,.

6. The element of claim 5 wherein said oxacyanine dye is 3- carboxymethyl-l -ethyloxa-2 -cyanine bromide.

7. The element of claim 5 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said imagereceiving element.

8. The element of claim 7 wherein said image-receiving element support layer is transparent.

9. The element of claim 8 wherein said photographic film 

2. an alkaline processing composition permeable and dyeable layer wherein said photosensitive and said image-receiving elements are adapted to be superposed, the support layers of each comprising the extremities of the superposed structure.
 2. The element of claim 1 wherein said acid functional substituent is -SO3H; -CO2H; -CO2 ; or -SO3H.
 3. The element of claim 2 wherein said oxacyanine dye is 3-carboxymethyl-1''-ethyloxa-2''-cyanine bromide.
 4. A photographic film unit which comprises, in combination: a photosensitive element having a diffusion transfer image-receiving element affixed at least one edge thereof, said photosensitive element comprising, as essential layers: a. a support layer; b. a cyan dye-containing layer associated with a red-sensitive silver halide emulsion; c. a magenta dye-containing layer associated with a green-sensitive silver halide emulsion; d. a yellow dye-containing layer associated with a blue-sensitive silver halide emulsion, each of said cyan, magenta and yellow dyes being silver halide developing agents and said blue-sensitive silver halide emulsion additionally including an oxacyanine dye of the formula:
 5. The element of claim 4 wherein said acid functional substituent is -SO3; -CO2H; -CO2 ; and -SO3 .
 6. The element of claim 5 wherein said oxacyanine dye is 3-carboxymethyl-1''-ethyloxa-2''-cyanine bromide.
 7. The element of claim 5 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said image-receiving element.
 8. The element of claim 7 wherein said image-receiving element support layer is transparent.
 9. The element of claim 8 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure. 